To provide an indwelling needle assembly causing no malfunction and enabling performing a stable procedure.SOLUTION: An indwelling needle assembly 1 is such that: only an outer needle 21 is further sent into a blood vessel and block of swing of an inner needle base 4 can be released by holding an enclosure 5 and punctuating an inner needle 3 and the outer needle 21 into an object region followed by pushing an inner cylinder operation part 66 of an inner cylinder 6 in the tip direction by the thumb or the forefinger of the hand holding the enclosure 5 support of the inner needle base 4 against a compression spring S (energization member) is released by swinging the inner needle base 4 only by drawing a switch operation part 74 of a switch 7 in the base end direction and the inner needle 3 is stored in the enclosure 5 by moving the inner needle base 4 in the base end direction with the compression spring S.SELECTED DRAWING: Figure 7【課題】誤作動が生じず、より安定した手技を行うことができる留置針組立体を提供する。【解決手段】留置針組立体1は、筐体5を保持して対象部位に内針3及び外針21を穿刺した後、筐体5を保持している手の親指又は人差し指で内筒6の内筒操作部66を先端方向に押すことで、外針21のみを血管内へさらに送出させると共に、内針基4の揺動の阻止を解除することができ、スイッチ7のスイッチ操作部74を基端方向に引くだけで内針基4を揺動させることで圧縮スプリングS(付勢部材)に抗した内針基4の支持が解除し、圧縮スプリングSにより内針基4を基端方向へ移動させ、内針3が筐体5内へ収容されるように構成される。【選択図】図7
